Medical nebulizers are used to deliver a prescribed medication, i.e., a medicated inhalant, as an aerosol to the lungs of a patient for direct absorption by the affected area. The nebulizer produces an aerosol either by forcing the liquid medicament through a nozzle, or by air atomization or by ultrasonic atomization. All three types of nebulizers can provide a convenient and efficient method for administering drugs to patients suffering from respiratory problems, such as, chronic pulmonary disease, asthma, and allergies. While all three types of nebulizers transform a liquid medicament into a mist, the ultrasonic nebulizers can produce the finest mist and are quieter than air atomizers which require a compressor.
The ultrasonic nebulizer can operate as a "patient demand" system. In simplest terms, a patient demand system pulls the medicament aerosol from a nebulizing chamber and delivers the aerosol to the patient only during inhalation. When the patient exhales or takes a break from treatment, the medication condenses in the chamber where it is re-nebulized until inhaled by the patient. The ultrasonic nebulizer operated as a patient demand system that is economical and efficient since the medication is delivered only to the affected area and only when needed. This minimizes the drug losses to the atmosphere and by delivery to unaffected areas and therefore eliminates the need for larger drug doses in order to compensate for loses. In addition, since the drug is more precisely delivered to the affected areas, the chance of an adverse drug reaction by the patient is reduced.
The size of the aerosol droplets is critical in patient treatment since finer droplets more deeply penetrate the affected area as well as increase the ability of the lungs to absorb such droplets. However, there has been no efficient device for ensuring that the size of the medicated aerosol particles which are delivered to the patient are relatively fine. In an ultrasonic nebulizer, a geyser containing a range of droplet sizes is formed. It is desirable to provide an ultrasonic nebulizer wherein only relatively fine droplets of a medicated aerosol are capable of being inhaled by a patient.